This invention relates to dispensers of materials that are liquid or semi-liquid, and capable of flowing, including but not limited to adhesives, sealants, caulks, greases, and paints. These materials will be referred to herein generally as fluid materials. Dispensers for these materials are known, and one known dispenser is the hot melt glue gun, which typically uses glue that can be formed into sticks rigid enough at room temperature to be urged into a melt chamber by a feed mechanism that grips the stick. Theses glue guns are limited, however, because they cannot utilize adhesives that are not sufficiently rigid at room temperatures. For example, these glue guns are not useful with adhesive compositions that are liquid or semi-liquid at room temperatures.
Dispensers are known for fluid materials, and these may take the form, for example, of the known caulking gun. In this structure, the caulk is placed in a tube that is received in a dispenser of some sort. There is a myriad of design approaches for these dispensers, and a typical dispenser has a plunger operated by a trigger mechanism whereby the plunger is urged into one end of the tube as the trigger is advanced to force the caulk from the opposite end of the tube by increasing the pressure in the tube. A problem with this type of dispenser is that the material in the tube may remain under pressure even after the motion of the plunger is terminated, which results in dripping from the nozzle. One factor in this problem is that the plunger is not necessarily fully released by relaxation of pressure on the trigger, which allows the material in the cartridge to remain under some degree of pressure.